1. Field of the Invention
The present invention relates to a method for producing artificial marble having a stripe pattern, and a continuous production apparatus thereof.
2. Description of the Related Art
Conventionally, artificial marble used in counters of wash stands, table tops and the like has been produced by curing a liquid resin. As a method for producing such artificial marble carrying patterns on the surface, Japanese Patent Application Publication (JP-B) No. 59-1568 and Japanese Patent Application Laid-Open (JP-A) No. 1317723 disclose a method in which a synthetic resin material of different colors is mixed by injecting a liquid resin into a molding cell.
However, according to these conventional methods, there are problems that reproducibility of pattern manifestation is deficient, and production yield for obtaining an excellent product is low. Further, when the product is used as artificial marble, the surface thereof is often shaved and therefore maintaining the surface pattern is required in this process. However, in many cases, the pattern disappears or changes significantly by shaving. Moreover, when an extraneous material is used for manifestation of a pattern, a difference in curing speed tends to occur and a difference in physical property between materials tends to occur. Consequently, the mechanical properties of the artificial marble may sometimes decrease as compared with that having no pattern.
The present inventors have suggested, as a method for solving the above-described problems, a method in which liquid resins having different colors are laminated in a molding cell, and comb-like tools are allowed to move in the molding cell before the resins are cured to produce artificial marble in JP-A No. 10-128771. According to this method, a stripe pattern having a clear appearance can be simply formed and control of this pattern is easy, and further, a pattern can also be formed continuously along with thickness direction.
However, the visual feeling is flat and a simple pattern is liable to be formed according to this method; therefore, the resulting artificial marble is not fully satisfactory from the standpoint of appearance as compared with natural wood materials and natural marble. Particularly, there is room for improvement in view of delicacy of the hue, depth, texture and a luxurious feeling present in natural substances such as natural wood, natural stone and the like.
Therefore, in JP-A No. 10-32384, a method is suggested in which a liquid resin containing a nonuniformly dispersed coloring agent is injected in the lowest layer of a molding cell and a comb-like tool is allowed to move in the molding cell, and production of artificial marble having a radial cut wood pattern with a delicate hue and natural appearance contained in wood or having a natural marble-like stripe pattern excellent in texture and deep feeling is made possible.
An object of the present invention is to provide a method for producing artificial marble wherein a pattern in which an interval of stripes varies in a more natural-like fashion can be formed and control of this pattern is easy.
Another object of the present invention is to provide a production method which can form artificial marble having a stripe pattern so that control of the pattern is easy and a more natural-like bleeding or diffusion is present at the boundary of the pattern.
Still another object of the present invention is to provide a method for producing artificial marble which can obtain a stripe pattern which can be formed continuously along the thickness direction and does not disappear even if the surface is shaved.
Further another object of the present invention is to provide a production apparatus for continuously carrying out industrial scale production of artificial marble having such a stripe pattern.
Namely, the present invention provides a method for producing artificial marble having a stripe pattern, comprising injecting liquid resins having different colors into a molding cell so that they are laminated to form two or more layers, then moving a comb-like tool through the laminated liquid resins while allowing the teeth to contact the bottom surface of the molding cell, then curing the liquid resins to form artificial marble, wherein the comb-like tool is allowed to move through the liquid resins while the interval between teeth of the comb-like tool is allowed to vary.
This method can be carried out by using a tool wherein the handle and teeth are connected via a soft member. Also, this method can be conducted by using a plurality of comb-like tools and allowing the comb-like tools to move through liquid resins while allowing the interval between teeth in the group of the comb-like tools to relatively vary.
Further, another aspect of the present invention is a method for producing artificial marble having a stripe pattern, comprising injecting liquid resins having different colors into a molding cell so that they are laminated to form two or more layers, then moving a comb-like tool through the laminated liquid resins while allowing the teeth to contact the bottom surface of the molding cell, then curing the liquid resins to form artificial marble, wherein the comb-like tool is allowed to move while allowing a bleeding forming means to contact the bottom surface of the molding cell following the track of the teeth of the comb-like tool.
As the above-described bleeding forming means, a member having a thickness and a weight to be buried into liquid resins can be used.
Furthermore, the present invention provides an apparatus for continuously producing artificial marble, comprising a molding cell which moves, a liquid resin supplying means for laminating liquid resins having different colors to form two or more layers on the molding cell, and a comb-like tool placed so that the teeth thereof are in contact with the bottom surface of the molding cell, wherein the liquid resin supplying means has a plurality of resin discharging ports, and at resin discharging ports for resins other than the lowest layer liquid resin, distributing plates are placed so that a liquid resin flows mainly to the cell moving direction and vertical direction thereof, and flowing to the reverse direction of the cell moving direction is prevented, and a non-stirring type mixer which mixes a liquid resin and a coloring agent is placed upstream of at least one resin discharging port.
In this production apparatus, a straightening plate can be further placed for imparting a constant flow directional property to the flow pattern of a liquid resin at the bottom surface of the molding cell, upstream of the liquid resin supplying means. As the above-described distributing plate, that having the combined shape of a shielding plate extending to vertical direction and a dividing plate inclined in the form of a semi-cone can be used.